The present invention relates to a phase detection system which is capable of detecting the difference in phase between two input signals and generating an output signal representative of the detected phase difference instantaneously without any delay in time.
In a prior art phase detection system of the type generating an output voltage representative of a phase difference between two input signals, the input signals are first converted into rectangular waveforms and the rectangular waveform signals are caused to pass through AND and OR gates so as to derive coincidence and noncoincidence signals. The coincidence and noncoincidence signals are smoothed through a low-pass filter so as to obtain an output voltage representative of a phase difference between the input signals. However, this system has the drawback that the phase detection can be made only once for each cycle; that is, the system cannot deliver a continuous phase difference information. In addition the prior art system must include a low-pass filter so that discontinuous phase difference information may be smoothed so that a time corresponding to a time constant of the low-pass filter is needed from an initial state before a correct output voltage can be derived. The prior art system has a further drawback that the time constant of the low-pass filter must be changed in order to detect the phase differences between input signals even when their frequencies vary.